The present invention relates to an athletic shoe midsole design and construction. More particularly, the invention relates to a midsole assembly where there are provided a midsole formed of soft elastic material and a corrugated sheet disposed in the midsole.
The sole of an athletic shoe used in various sports is generally comprised of a midsole and an outsole fitted under the midsole, directly contacting with the ground. The midsole is typically formed of soft elastic material in order to ensure adequate cushioning properties.
Running stability as well as adequate cushioning properties are required in athletic shoes. There is a need to prevent shoes from being deformed excessively in the lateral or transverse direction when contacting with the ground.
As shown in Japanese Utility Model Application Publication No. 61-6804, the applicant of the present invention proposes a midsole assembly having a corrugated sheet therein, which can prevent such an excessive lateral deformation of shoes.
The midsole assembly shown in the above publication incorporates a corrugated sheet in a heel portion of a midsole and it can produce resistant force preventing the heel portion of a midsole from being deformed laterally or transversely when a shoe contacts with the ground. Thus, the transverse deformation of the heel portion of a shoe is prevented.
Generally, by inserting a corrugated sheet, compressive hardness (or hardness to deformation against the compressive force) of the whole midsole becomes high and the midsole tends to be less deformed in the vertical direction as well as transverse direction. Therefore, when the corrugated sheet is interposed in the midsole, the midsole portion where adequate cushioning properties is required may show less cushioning properties, or an athlete may have an unpleasant feeling around the sole of a foot in the shoes when the shoes come in contact with the ground.
On the other hand, a corrugated sheet is generally composed of a homogeneous material, but if the compressive hardness can be changed according to the regions of the corrugated sheet, detailed and delicate adjustments can be possible with regard to the contradictory requirements of preventing lateral deformation and achieving cushioning properties on landing.
The object of the present invention is to provide a midsole assembly for an athletic shoe that can secure not only running stability but also cushioning properties. Another object of the present invention is to provide a midsole assembly for an athletic shoe that can secure running stability and make foot sole contact feeling pleasant. A further object of the present invention is to provide a midsole assembly for an athletic shoe that can make detailed and delicate adjustments with regard to the contradictory requirements of preventing lateral deformation and achieving cushioning properties on landing.
The present invention provides a midsole assembly for an athletic shoe.
In one embodiment, a midsole assembly comprises a midsole formed of soft elastic material and a corrugated sheet disposed in the heel portion to the forefoot portion of the midsole. The midsole is composed of an upper midsole placed on the upper side of the corrugated sheet and a lower midsole placed on the lower side of the corrugated sheet. The upper midsole has a different hardness from that of the lower midsole.
A second embodiment provides a midsole assembly according to the first embodiment, wherein the upper and lower midsoles are comprised of the same material.
A third embodiment provides a midsole assembly according to the first embodiment, wherein the upper and lower midsoles are comprised of different materials.
A fourth embodiment provides a midsole assembly according to the first embodiment, wherein the heel portion of the upper midsole has a lower hardness than the heel portion of the lower midsole.
A fifth embodiment provides a midsole assembly according to the first embodiment, wherein the heel portion of the lower midsole has a lower hardness than the heel portion of the upper midsole.
A sixth embodiment provides a midsole assembly according to the first embodiment, wherein the forefoot portion of the upper midsole has a lower hardness than the forefoot portion of the lower midsole.
A seventh embodiment provides a midsole assembly according to the first embodiment, wherein the forefoot portion of the lower midsole has a lower hardness than the forefoot portion of the upper midsole.
An eighth embodiment provides a midsole assembly according to the first embodiment, wherein a higher elastic member than the corrugated sheet is provided along the outer circumference of the heel portion of the corrugated sheet.
A ninth embodiment provides a midsole assembly according to the first embodiment, wherein a lower elastic portion than the corrugated sheet is provided on the heel central region of the corrugated sheet.
A tenth embodiment provides a midsole assembly according to the first embodiment, wherein a higher elastic member than the corrugated sheet is provided along the outer circumference of the heel portion of the corrugated sheet. Also, a lower elastic portion than the corrugated sheet is provided on the heel central region of the corrugated sheet.
The higher elastic member may be comprised of a fiber-reinforced plastic sheet or a metal plate, as is respectively described in an eleventh or twelfth embodiment.
The higher elastic member may be bonded to the corrugated sheet, or may be injection molded with the corrugated sheet, as is respectively described in a thirteenth or fourteenth embodiment.
The lower elastic portion may be comprised of a plurality of holes formed in the corrugated sheet, as is described in a fifteenth embodiment. Alternatively, as is described in a sixteenth embodiment, the lower elastic portion may be comprised of a meshed sheet that is injection molded with the corrugated sheet.
A seventeenth embodiment provides a midsole assembly according to the first embodiment, wherein a lower elastic portion is provided at the forefoot portion of the corrugated sheet.
The lower elastic portion may be comprised of a plurality of holes formed in the corrugated sheet, as is described in an eighteenth embodiment. In the alternative, as is described in a nineteenth embodiment, the lower elastic portion may be comprised of a meshed sheet that is injection molded with the corrugated sheet.
The forefoot portion of the corrugated sheet may include a groove that extends in the transverse direction, as is described in a twentieth embodiment.
A twenty-first embodiment provides a midsole assembly according to the first embodiment, wherein a higher elastic member than the corrugated sheet is provided at the plantar arch portion of the corrugated sheet.
The higher elastic member may be comprised of a fiber-reinforced plastic sheet, or a metal plate, as is respectively described in a twenty-second or twenty-third embodiment.
The higher elastic member may be bonded to the corrugated sheet, as is described in a twenty-fourth embodiment. Alternatively, the higher elastic member may be injection molded with the corrugated sheet, as is described in a twenty-fifth embodiment.
A twenty-sixth embodiment provides a midsole assembly according to the first embodiment, wherein the amplitude of the wave configuration of the corrugated sheet is larger on the medial and lateral sides of the heel portion of the corrugated sheet, and smaller at the heel central portion.
A twenty-seventh embodiment provides a midsole assembly according to the first embodiment, wherein the phase of the wave configuration of the corrugated sheet is offset by one-half pitch between the medial and lateral sides of the heel portion of the corrugated sheet.
In the first embodiment, a corrugated sheet is disposed in the heel portion to the forefoot portion of the midsole.
Thus, the regions from the heel portion to the forefoot portion of the midsole tend to be less deformed in the lateral or transverse direction at the time of landing on the ground. As a result, the forefoot portion as well as the heel portion can be prevented from being laterally deformed and running stability can be secured.
Moreover, because the corrugated sheet is provided in the forefoot portion, the bending or turning direction of the forefoot portion can be controlled. That is, when the wavelength of the wave configuration of the corrugated sheet is different between the medial and lateral sides of the forefoot portion, the ridge lines of the wave configuration are disposed in a fan shape. Thus, when an athlete lands on the ground with the heel portion to the toe portion, weight transfer path or load path of the shoe sole can nearly coincide with the director line of the wave configuration of the corrugated sheet.
Thus, the heel portion flexibly deforms according to the weight transfer, and smooth weight transfer and stable grip properties can be secured with the cushioning properties and running stability maintained on the heel contact with the ground.
Furthermore, according to the first embodiment, hardness of the upper midsole disposed on the upper side of the corrugated sheet is different from the hardness of the lower midsole disposed on the lower side of the corrugated sheet. For example, when the hardness of the lower midsole is lowered, the cushioning properties are improved. On the other hand, when the hardness of the upper midsole is lowered, contact feeling of the foot sole of an athlete becomes better.
In addition, difference of the hardness of the upper and lower midsoles is preferably about 10 degrees at Asker C scale.
The upper midsole and lower midsole may be composed of the same material, as shown in the second embodiment. Alternatively, the upper and lower midsole may be composed of the different materials, as shown in the third embodiment.
When the upper midsole and lower midsole are made of the same material, in altering the hardness of the upper and lower midsoles, expansion ratios of the upper and lower midsoles are made different. That is, a higher expansion ratio decreases hardness, whereas a lower expansion ratio increases hardness.
Alternatively, by altering the characteristics of the material itself, hardness can be changed. That is, adding plasticizer in the material or altering the volume of adjunct of the plasticizer can be employed. Adding plasticizer lowers the hardness of the material and increasing the volume of adjunct of the plasticizer further lowers its hardness. Moreover, hardness can be changed by altering the degree of polymerization, and thus changing the molecular weight.
In addition, when the upper and lower midsoles are made of different materials, the hardness of the upper and lower midsoles can be altered by adopting the similar method mentioned above.
According to the fourth embodiment, because the hardness of the heel portion of the upper midsole is lower than that of the heel portion of the lower midsole, contact feeling of the heel portion of a shoes wearer is improved at the time of landing on the ground and the cushioning properties are advanced.
According to the fifth embodiment, because the hardness of the heel portion of the lower midsole is lower than that of the heel portion of the upper midsole, shock load from the contact surface with the ground to the heel portion at the time of landing is relieved at the lower midsole and cushioning properties of the heel portion are improved. On the other hand, since the upper midsole, which has a higher hardness than the lower midsole, is hard to be deformed and is thus relatively less deformed, the corrugated sheet generates a resistance force against the load applied to the upper midsole from the foot sole of a shoes wearer, and as a result, the heel portion is prevented from being deformed laterally or transversely after landing.
According to the sixth embodiment, because the hardness of the forefoot portion of the upper midsole is lower than that of the forefoot portion of the lower midsole, contact feeling of the forefoot portion of a shoes wearer at the time of landing becomes pleasant and cushioning properties are improved, and flexibility of the forefoot portion as well is improved.
According to the seventh embodiment, because the hardness of the forefoot portion of the lower midsole is lower than that of the forefoot portion of the upper midsole, cushioning properties are improved in such a way that shock load from the contact surface with the ground to the forefoot portion at the time of landing is relieved at the lower midsole. On the other hand, since the upper midsole tends to be relatively less deformed, the corrugated sheet develops its natural function against the load applied from the foot sole of a shoes wearer to the upper midsole and as a result, the forefoot portion can be prevented from being deformed in the transverse direction after landing.
According to the eighth embodiment, a higher elastic member is disposed along the outer circumference of the heel portion of the corrugated sheet. Here, xe2x80x9chigher elasticxe2x80x9d means having a higher modulus of elasticity.
Thus, the compressive hardness (or hardness to deformation against the compressive force) of the midsole is made higher at the outer circumference of the heel portion, and as a result, even in the athletics where severe lateral movements are included, deformation of a shoe after landing can be prevented and running stability can be secured. Moreover, in that the heel of a foot can be restrained from unnecessarily sinking into the midsole, loss of athletic power is lessened.
On the other hand, because flexibility of the midsole is maintained in some degree at the heel central portion, which has a relatively small compressive hardness compared to the heel outer circumferential portion, cushioning properties on landing can be ensured at this heel central portion.
In this way, two contradictory requirements of preventing lateral deformation and ensuring cushioning properties can be satisfied.
Additionally, in this case, when a material of relatively small elasticity as a corrugated sheet is used, the heel central portion of the midsole can be made more flexible and cushioning properties can be more improved.
Moreover, specifically, when the hardness of the heel portion of the lower midsole is lower than that of the heel portion of the upper midsole, lateral or transverse deformation of shoes after landing can be more securely prevented with less deformation of the upper midsole and running stability can be further improved.
According to the ninth embodiment, a lower elastic portion than the corrugated sheet is provided in the heel central portion of the corrugated sheet. Here, xe2x80x9clower elasticxe2x80x9d means having a lower modulus of elasticity.
Thus, the compressive hardness of the midsole is lowered at the heel central portion, and as a result, flexibility of the midsole is maintained and cushioning properties on landing can be advanced.
On the other hand, at the outer circumferential region of the heel portion, which has a relatively high compressive hardness compared to the heel central portion, lateral deformation after landing can be prevented and running stability can be secured.
Consequently, in this case as well, similarly to the eighth embodiment, two contradictory requirements of prevention of transverse deformation and securement of cushioning properties can be satisfied at the heel portion.
In addition, specifically, when the hardness of the heel portion of the lower midsole is lower than that of the heel portion of the upper midsole, cushioning properties can be further improved with the cushioning performance of the lower midsole.
According to the tenth embodiment, a higher elastic member than the corrugated sheet is placed along the outer circumference of the heel portion of the corrugated sheet and a lower elastic portion than the corrugated sheet is provided at the heel central portion of the corrugated sheet.
Thus, lateral or transverse deformation after landing can be prevented at the heel outer circumferential portion having a greater compressive hardness, and cushioning properties on landing can be secured at the heel central portion having a smaller compressive hardness.
According to the eleventh embodiment, a higher elastic member is composed of a fiber-reinforced plastic sheet. This fiber-reinforced plastic (FRP) sheet comprises reinforcement fiber and matrix resin. Reinforcement fiber may be carbon fiber, aramid fiber, glass fiber or the like. Matrix resin may be thermoplastic or thermosetting resin. In this way, the corrugated sheet has improved elasticity and durability, and can bear a prolonged use.
A higher elastic member may be composed of a metal plate such as SUS (or stainless steel) plate, super elastic alloy plate or the like, as shown in the twelfth embodiment.
A higher elastic member may be bonded to the corrugated sheet, as shown in the thirteenth embodiment. In the alternative, as shown in the fourteenth embodiment, a higher elastic member may be injection molded together with the corrugated sheet.
A lower elastic portion may be comprised of a plurality of holes formed in the corrugated sheet, as shown in the fifteenth embodiment. Alternatively, as shown in the sixteenth embodiment, a lower elastic portion may be comprised of a meshed sheet that is injection molded together with the corrugated sheet.
According to the seventeenth embodiment, a lower elastic portion than the corrugated sheet is provided at the forefoot portion of the corrugated sheet.
Thus, the compressive hardness of the midsole is lowered at the forefoot portion, and as a result, cushioning properties of the forefoot portion can be secured at the time of landing. Moreover, flexibility of the forefoot portion can be improved and turnability of the forefoot portion can be advanced.
Furthermore, in this case, when the hardness of the forefoot portion of the upper midsole is lower than that of the forefoot portion of the lower midsole, flexibility of the forefoot portion can be further improved.
In addition, the forefoot portion of the corrugated sheet may be formed with a plurality of holes, which is formed in the corrugated sheet, as shown in the eighteenth embodiment. The forefoot portion of the corrugated sheet may be comprised of a meshed sheet that is injection molded together with the corrugated sheet, as shown in the nineteenth embodiment.
As shown in the twentieth embodiment, a groove extending in the lateral or transverse direction may be formed at the forefoot portion of the corrugated sheet. In this case, flexibility of the forefoot portion of the midsole can be further improved and control of turning or bending direction can be conducted with ease.
That is, when the spaces of the grooves at the forefoot portion are made different between the medial and lateral sides, grooves are disposed in a fan shape, thereby allowing the weight transfer path (or load path) at the shoe sole surface to nearly conform with the director line of the grooves.
Thus, the heel portion flexibly deforms according to the weight transfer with the cushioning properties and running stability maintained at the time of landing. As a result, smooth weight transfer and secure grip properties can be ensured.
According to the twenty-first embodiment, a higher elastic member than the corrugated sheet is disposed at the plantar arch portion of the corrugated sheet. Thus, so-called shank effect can be developed and rigidity of the plantar arch portion can be improved. As a result, after landing, lateral deformation of the plantar arch portion of the midsole can be prevented and running stability can be secured.
A higher elastic member may be composed of a fiber-reinforced plastic sheet, as shown in the twenty-second embodiment. Or a higher elastic member may be composed of a metal plate, as shown in the twenty-third embodiment.
A higher elastic member may be bonded to the corrugated sheet, as shown in the twenty-fourth embodiment. In alternative, as shown in the twenty-fifth embodiment, a higher elastic member may be injection molded together with the corrugated sheet.
According to the twenty-sixth embodiment, the amplitude of the wave configuration of the corrugated sheet is larger on the medial and lateral sides of the heel portion of the corrugated sheet, and smaller at the heel central portion.
Thus, flexibility of the midsole is maintained at the heel central portion having a small amplitude and the compressive hardness of the midsole is made greater on the medial and lateral sides having a large amplitude. As a result, cushioning properties on landing can be secured at the heel central portion, and lateral or transverse deformation of the heel portion after landing can be prevented and running stability can be improved.
In this manner, similarly to the eighth and ninth embodiments, two contradictory requirements of prevention of lateral deformation and securement of cushioning properties can be satisfied at the heel portion.
In this case, when the hardness of the heel portion of the upper midsole is lower than that of the heel portion of the lower midsole, cushioning properties can be advanced with foot contact feeling in the shoes on landing made pleasant.
On the contrary, when the hardness of the heel portion of the lower midsole is lower than that of the heel portion of the upper midsole, cushioning properties of the lower midsole can be further improved.
According to the twenty-seventh embodiment, phase of the wave configuration of the corrugated sheet is offset by one-half pitch between the medial and lateral sides of the heel portion of the corrugated sheet.
In this case, as regards the wave configuration of the heel medial side to the heel lateral side, the crest at the medial portion is positioned against the trough at the lateral portion. Similarly, the trough at the medial portion is positioned against the crest at the lateral portion.
Thus, the ridge line of the wave configuration at the heel medial portion gradually declines as it goes toward the heel central portion, and when the ridge line crosses the heel central portion, the amplitude of the wave configuration becomes zero. As the ridge line goes over the heel central portion, it becomes a trough line, and the trough line declines as it goes toward the heel lateral portion.
Similarly, the ridge line of the wave configuration at the heel lateral portion gradually declines as it goes toward the heel central portion, and when the ridge line crosses the heel central portion, the amplitude of the wave configuration becomes zero. As the ridge line goes over the heel central portion, it becomes a trough line, and the trough line declines as it goes toward the heel medial portion.
In this way, because the amplitude of the wave configuration is zero at the central portion between the heel medial and lateral sides, similarly to the twenty-sixth embodiment, flexibility of the midsole is maintained at the heel central portion and the compressive hardness of the midsole is made greater at the medial and lateral sides of the heel portion. As a result, cushioning properties on landing can be secured at the heel central portion, and transverse deformation after landing can be prevented at the heel medial and lateral sides, thereby improving the running stability.
In this case, when the hardness of the heel portion of the upper midsole is lower than that of the heel portion of the lower midsole, cushioning properties can be improved with foot contact feeling in shoes at the time of landing made pleasant.
On the contrary, when the hardness of the heel portion of the lower midsole is lower than that of the heel portion of the upper midsole, cushioning properties of the lower midsole can be further improved.